A very common problem with many below ground basement walls is that water tends to build up on the outside of such basement walls which causes a very high hydrostatic pressure against the wall. If this pressure becomes significant, it causes the wall to be pushed into the basement to some extent. Commonly, a large horizontal crack will appear in the wall. Besides the obvious problem of the unsightly nature of the crack, it will also permit water into the basement and if the hydrostatic pressure continues to increase the wall could eventually collapse.
The main reason a walls lateral strength is compromised is due to poor drainage or negative grade adjacent to the basement wall. When it rains or snow melts, this water accumulates next to the wall rather than draining away over the surface. When water is allowed to collect next to the wall it soaks into the soil, such that when the moisture content of expansive soil is increased, the soil expands. This expansion can put large amounts of stress on the side of the wall causing it to break in the middle and bow in. At this point, the lateral strength of the wall is compromised leaving it susceptible to failure especially if large amounts of rain or melting snow persist. When the soil undergoes significant expansion when wet and shrinkage when it dries, this can create a gap between the wall and the soil, the gap usually fills with loose soil adding to the negative grade causing magnifying the problem. It becomes a vicious cycle, and over time the wall is sure to fall in. The grade eventually gets worse causing more of a soaking action, causing more stress on the wall. When a wall anchor is installed and the grade raised, the walls lateral strength may be restored, and it can resist the forces exerted by the expanding soil. When the climate cycles through wet and dry periods, the soils natural expansion and contraction is thereby minimized because the water runs away leaving the soil adjacent to the wall to have a relatively consistent moisture content. Given this, wall anchors need to be adjustable allowing them to be tightened during dry weather. When the soil dries, it shrinks away from the wall leaving a gap, so the wall can easily be pulled straight by tightening the anchors.
The most common accepted methods and apparatus for straightening a basement wall are illustrated in U.S. Pat. Nos. 4,189,891 and 4,970,835.
The former patent relates to a method for anchoring and straightening a wall wherein a hole is formed in the ground at a distance from the wall and an opening is provided in the wall from the inside below ground level. Then an elongated rod member is positioned through the opening in the wall and forced through the ground so that one end of the member extends into the hole previously formed. An anchor structure, such as an anchor plate, is secured to one end of the rod member in the hole, and a wall plate is attached to the other end of the elongated rod member inside and against the wall. The wall plate is then forced against the wall by use of a threaded attaching mechanism for thereby straightening the wall.
The wall anchoring and straightening device of the latter referenced patent is in many ways similar but eliminates the need for digging the hole into the earth at a spaced distance from the wall. This device comprises a horizontal elongated rod member having a chisel point end which is driven through the foundation wall into the earth and carries a plurality of pivotal spade arms adjacent the chisel point. The end of the rod member, which is positioned at the interior of the wall, is provided with threads. In similar fashion, a wall plate is forced against the wall by a nut which is tightened to pull the rod member and chisel arm and spade arms closer to the foundation wall which thereby firmly causes the spade arms to spread and dig into the surrounding earth to provide an anchor. Further tightening of the nut causes the wall plate to be forced against the wall and to straighten the wall.